Implement debugging of WOW64 processes in gdbserver

gdbserver/ChangeLog:

2020-04-30  Hannes Domani  <ssbssa@yahoo.de>

	* configure.srv <x86_64-*-mingw*, x86_64-*-cygwin*> (srv_tgtobj):
	Add arch/i386.o.
	* win32-arm-low.cc (arm_num_regs): New function.
	(struct win32_target_ops): Use arm_num_regs.
	* win32-i386-low.cc (win32_get_current_dr): Adapt for WOW64
	processes.
	(i386_get_thread_context): Likewise.
	(i386_prepare_to_resume): Likewise.
	(i386_thread_added): Likewise.
	(i386_single_step): Likewise.
	(i386_fetch_inferior_register): Likewise.
	(i386_store_inferior_register): Likewise.
	(i386_arch_setup): Likewise.
	(i386_win32_num_regs): New function.
	(struct win32_target_ops): Use i386_win32_num_regs.
	* win32-low.cc (win32_get_thread_context): Adapt for WOW64
	processes.
	(win32_require_context): Likewise.
	(child_add_thread): Likewise.
	(do_initial_child_stuff): Likewise.
	(continue_one_thread): Likewise.
	(win32_process_target::resume): Likewise.
	(load_psapi): Likewise.
	(win32_add_all_dlls): Likewise.
	(maybe_adjust_pc): Likewise.
	(win32_process_target::qxfer_siginfo): Likewise.
	(initialize_low): Likewise.
	* win32-low.h (struct win32_target_ops): Change num_regs to
	callback function.

6 files changed, 404 insertions, 62 deletions

diff --git a/gdbserver/ChangeLog b/gdbserver/ChangeLog
index 3b5fd99..4853463 100644
--- a/gdbserver/ChangeLog
+++ b/gdbserver/ChangeLog
@@ -1,3 +1,35 @@
+2020-04-30  Hannes Domani  <ssbssa@yahoo.de>
+
+	* configure.srv <x86_64-*-mingw*, x86_64-*-cygwin*> (srv_tgtobj):
+	Add arch/i386.o.
+	* win32-arm-low.cc (arm_num_regs): New function.
+	(struct win32_target_ops): Use arm_num_regs.
+	* win32-i386-low.cc (win32_get_current_dr): Adapt for WOW64
+	processes.
+	(i386_get_thread_context): Likewise.
+	(i386_prepare_to_resume): Likewise.
+	(i386_thread_added): Likewise.
+	(i386_single_step): Likewise.
+	(i386_fetch_inferior_register): Likewise.
+	(i386_store_inferior_register): Likewise.
+	(i386_arch_setup): Likewise.
+	(i386_win32_num_regs): New function.
+	(struct win32_target_ops): Use i386_win32_num_regs.
+	* win32-low.cc (win32_get_thread_context): Adapt for WOW64
+	processes.
+	(win32_require_context): Likewise.
+	(child_add_thread): Likewise.
+	(do_initial_child_stuff): Likewise.
+	(continue_one_thread): Likewise.
+	(win32_process_target::resume): Likewise.
+	(load_psapi): Likewise.
+	(win32_add_all_dlls): Likewise.
+	(maybe_adjust_pc): Likewise.
+	(win32_process_target::qxfer_siginfo): Likewise.
+	(initialize_low): Likewise.
+	* win32-low.h (struct win32_target_ops): Change num_regs to
+	callback function.
+
 2020-04-27  Simon Marchi  <simon.marchi@efficios.com>
 
 	* configure.ac: Remove check for fs_base/gs_base in
diff --git a/gdbserver/configure.srv b/gdbserver/configure.srv
index 7acf229..9a027e4 100644
--- a/gdbserver/configure.srv
+++ b/gdbserver/configure.srv
@@ -397,14 +397,14 @@ case "${gdbserver_host}" in
 			srv_tgtobj="x86-low.o nat/x86-dregs.o i387-fp.o"
 			srv_tgtobj="${srv_tgtobj} win32-low.o win32-i386-low.o"
 			srv_tgtobj="${srv_tgtobj} nat/windows-nat.o"
-			srv_tgtobj="${srv_tgtobj} arch/amd64.o"
+			srv_tgtobj="${srv_tgtobj} arch/amd64.o arch/i386.o"
 			srv_mingw=yes
 			;;
   x86_64-*-cygwin*)	srv_regobj=""
 			srv_tgtobj="x86-low.o nat/x86-dregs.o i387-fp.o"
 			srv_tgtobj="${srv_tgtobj} win32-low.o win32-i386-low.o"
 			srv_tgtobj="${srv_tgtobj} nat/windows-nat.o"
-			srv_tgtobj="${srv_tgtobj} arch/amd64.o"
+			srv_tgtobj="${srv_tgtobj} arch/amd64.o arch/i386.o"
 			;;
 
   xtensa*-*-linux*)	srv_regobj=reg-xtensa.o
diff --git a/gdbserver/win32-arm-low.cc b/gdbserver/win32-arm-low.cc
index 238ee4b..aacf2cd 100644
--- a/gdbserver/win32-arm-low.cc
+++ b/gdbserver/win32-arm-low.cc
@@ -111,6 +111,14 @@ arm_arch_setup (void)
   win32_tdesc = tdesc_arm;
 }
 
+/* Implement win32_target_ops "num_regs" method.  */
+
+static int
+arm_num_regs (void)
+{
+  return sizeof (mappings) / sizeof (mappings[0]),
+}
+
 /* Correct in either endianness.  We do not support Thumb yet.  */
 static const unsigned long arm_wince_breakpoint = 0xe6000010;
 #define arm_wince_breakpoint_len 4
@@ -138,7 +146,7 @@ arm_win32_set_pc (struct regcache *regcache, CORE_ADDR pc)
 
 struct win32_target_ops the_low_target = {
   arm_arch_setup,
-  sizeof (mappings) / sizeof (mappings[0]),
+  arm_num_regs,
   NULL, /* initial_stuff */
   arm_get_thread_context,
   NULL, /* prepare_to_resume */
diff --git a/gdbserver/win32-i386-low.cc b/gdbserver/win32-i386-low.cc
index 48893af..389ec49 100644
--- a/gdbserver/win32-i386-low.cc
+++ b/gdbserver/win32-i386-low.cc
@@ -80,18 +80,40 @@ win32_get_current_dr (int dr)
 
   win32_require_context (th);
 
+#ifdef __x86_64__
+#define RET_DR(DR)				\
+  case DR:					\
+    return th->wow64_context.Dr ## DR
+
+  if (wow64_process)
+    {
+      switch (dr)
+	{
+	  RET_DR (0);
+	  RET_DR (1);
+	  RET_DR (2);
+	  RET_DR (3);
+	  RET_DR (6);
+	  RET_DR (7);
+	}
+    }
+  else
+#undef RET_DR
+#endif
 #define RET_DR(DR)				\
   case DR:					\
     return th->context.Dr ## DR
 
-  switch (dr)
     {
-      RET_DR (0);
-      RET_DR (1);
-      RET_DR (2);
-      RET_DR (3);
-      RET_DR (6);
-      RET_DR (7);
+      switch (dr)
+	{
+	  RET_DR (0);
+	  RET_DR (1);
+	  RET_DR (2);
+	  RET_DR (3);
+	  RET_DR (6);
+	  RET_DR (7);
+	}
     }
 
 #undef RET_DR
@@ -219,12 +241,27 @@ i386_get_thread_context (windows_thread_info *th)
   static DWORD extended_registers = CONTEXT_EXTENDED_REGISTERS;
 
  again:
-  th->context.ContextFlags = (CONTEXT_FULL
-			      | CONTEXT_FLOATING_POINT
-			      | CONTEXT_DEBUG_REGISTERS
-			      | extended_registers);
+#ifdef __x86_64__
+  if (wow64_process)
+    th->wow64_context.ContextFlags = (CONTEXT_FULL
+				      | CONTEXT_FLOATING_POINT
+				      | CONTEXT_DEBUG_REGISTERS
+				      | extended_registers);
+  else
+#endif
+    th->context.ContextFlags = (CONTEXT_FULL
+				| CONTEXT_FLOATING_POINT
+				| CONTEXT_DEBUG_REGISTERS
+				| extended_registers);
 
-  if (!GetThreadContext (th->h, &th->context))
+  BOOL ret;
+#ifdef __x86_64__
+  if (wow64_process)
+    ret = win32_Wow64GetThreadContext (th->h, &th->wow64_context);
+  else
+#endif
+    ret = GetThreadContext (th->h, &th->context);
+  if (!ret)
     {
       DWORD e = GetLastError ();
 
@@ -247,13 +284,28 @@ i386_prepare_to_resume (windows_thread_info *th)
 
       win32_require_context (th);
 
-      th->context.Dr0 = dr->dr_mirror[0];
-      th->context.Dr1 = dr->dr_mirror[1];
-      th->context.Dr2 = dr->dr_mirror[2];
-      th->context.Dr3 = dr->dr_mirror[3];
-      /* th->context.Dr6 = dr->dr_status_mirror;
-	 FIXME: should we set dr6 also ?? */
-      th->context.Dr7 = dr->dr_control_mirror;
+#ifdef __x86_64__
+      if (wow64_process)
+	{
+	  th->wow64_context.Dr0 = dr->dr_mirror[0];
+	  th->wow64_context.Dr1 = dr->dr_mirror[1];
+	  th->wow64_context.Dr2 = dr->dr_mirror[2];
+	  th->wow64_context.Dr3 = dr->dr_mirror[3];
+	  /* th->wow64_context.Dr6 = dr->dr_status_mirror;
+	     FIXME: should we set dr6 also ?? */
+	  th->wow64_context.Dr7 = dr->dr_control_mirror;
+	}
+      else
+#endif
+	{
+	  th->context.Dr0 = dr->dr_mirror[0];
+	  th->context.Dr1 = dr->dr_mirror[1];
+	  th->context.Dr2 = dr->dr_mirror[2];
+	  th->context.Dr3 = dr->dr_mirror[3];
+	  /* th->context.Dr6 = dr->dr_status_mirror;
+	     FIXME: should we set dr6 also ?? */
+	  th->context.Dr7 = dr->dr_control_mirror;
+	}
 
       th->debug_registers_changed = false;
     }
@@ -268,11 +320,14 @@ i386_thread_added (windows_thread_info *th)
 static void
 i386_single_step (windows_thread_info *th)
 {
-  th->context.EFlags |= FLAG_TRACE_BIT;
+#ifdef __x86_64__
+  if (wow64_process)
+    th->wow64_context.EFlags |= FLAG_TRACE_BIT;
+  else
+#endif
+    th->context.EFlags |= FLAG_TRACE_BIT;
 }
 
-#ifndef __x86_64__
-
 /* An array of offset mappings into a Win32 Context structure.
    This is a one-to-one mapping which is indexed by gdb's register
    numbers.  It retrieves an offset into the context structure where
@@ -280,8 +335,12 @@ i386_single_step (windows_thread_info *th)
    An offset value of -1 indicates that Win32 does not provide this
    register in it's CONTEXT structure.  In this case regptr will return
    a pointer into a dummy register.  */
+#ifdef __x86_64__
+#define context_offset(x) (offsetof (WOW64_CONTEXT, x))
+#else
 #define context_offset(x) ((int)&(((CONTEXT *)NULL)->x))
-static const int mappings[] = {
+#endif
+static const int i386_mappings[] = {
   context_offset (Eax),
   context_offset (Ecx),
   context_offset (Edx),
@@ -328,10 +387,10 @@ static const int mappings[] = {
 };
 #undef context_offset
 
-#else /* __x86_64__ */
+#ifdef __x86_64__
 
 #define context_offset(x) (offsetof (CONTEXT, x))
-static const int mappings[] =
+static const int amd64_mappings[] =
 {
   context_offset (Rax),
   context_offset (Rbx),
@@ -402,7 +461,21 @@ static void
 i386_fetch_inferior_register (struct regcache *regcache,
 			      windows_thread_info *th, int r)
 {
-  char *context_offset = (char *) &th->context + mappings[r];
+  const int *mappings;
+#ifdef __x86_64__
+  if (!wow64_process)
+    mappings = amd64_mappings;
+  else
+#endif
+    mappings = i386_mappings;
+
+  char *context_offset;
+#ifdef __x86_64__
+  if (wow64_process)
+    context_offset = (char *) &th->wow64_context + mappings[r];
+  else
+#endif
+    context_offset = (char *) &th->context + mappings[r];
 
   long l;
   if (r == FCS_REGNUM)
@@ -424,7 +497,22 @@ static void
 i386_store_inferior_register (struct regcache *regcache,
 			      windows_thread_info *th, int r)
 {
-  char *context_offset = (char *) &th->context + mappings[r];
+  const int *mappings;
+#ifdef __x86_64__
+  if (!wow64_process)
+    mappings = amd64_mappings;
+  else
+#endif
+    mappings = i386_mappings;
+
+  char *context_offset;
+#ifdef __x86_64__
+  if (wow64_process)
+    context_offset = (char *) &th->wow64_context + mappings[r];
+  else
+#endif
+    context_offset = (char *) &th->context + mappings[r];
+
   collect_register (regcache, r, context_offset);
 }
 
@@ -439,15 +527,32 @@ i386_arch_setup (void)
 #ifdef __x86_64__
   tdesc = amd64_create_target_description (X86_XSTATE_SSE_MASK, false,
 					   false, false);
-  const char **expedite_regs = amd64_expedite_regs;
-#else
+  init_target_desc (tdesc, amd64_expedite_regs);
+  win32_tdesc = tdesc;
+#endif
+
   tdesc = i386_create_target_description (X86_XSTATE_SSE_MASK, false, false);
-  const char **expedite_regs = i386_expedite_regs;
+  init_target_desc (tdesc, i386_expedite_regs);
+#ifdef __x86_64__
+  wow64_win32_tdesc = tdesc;
+#else
+  win32_tdesc = tdesc;
 #endif
+}
 
-  init_target_desc (tdesc, expedite_regs);
+/* Implement win32_target_ops "num_regs" method.  */
 
-  win32_tdesc = tdesc;
+static int
+i386_win32_num_regs (void)
+{
+  int num_regs;
+#ifdef __x86_64__
+  if (!wow64_process)
+    num_regs = sizeof (amd64_mappings) / sizeof (amd64_mappings[0]);
+  else
+#endif
+    num_regs = sizeof (i386_mappings) / sizeof (i386_mappings[0]);
+  return num_regs;
 }
 
 /* Implement win32_target_ops "get_pc" method.  */
@@ -496,7 +601,7 @@ i386_win32_set_pc (struct regcache *regcache, CORE_ADDR pc)
 
 struct win32_target_ops the_low_target = {
   i386_arch_setup,
-  sizeof (mappings) / sizeof (mappings[0]),
+  i386_win32_num_regs,
   i386_initial_stuff,
   i386_get_thread_context,
   i386_prepare_to_resume,
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 5a6f0df..4eb63b7 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -88,15 +88,30 @@ static int soft_interrupt_requested = 0;
    by suspending all the threads.  */
 static int faked_breakpoint = 0;
 
+#ifdef __x86_64__
+bool wow64_process = false;
+#endif
+
 const struct target_desc *win32_tdesc;
+#ifdef __x86_64__
+const struct target_desc *wow64_win32_tdesc;
+#endif
 
-#define NUM_REGS (the_low_target.num_regs)
+#define NUM_REGS (the_low_target.num_regs ())
 
 typedef BOOL (WINAPI *winapi_DebugActiveProcessStop) (DWORD dwProcessId);
 typedef BOOL (WINAPI *winapi_DebugSetProcessKillOnExit) (BOOL KillOnExit);
 typedef BOOL (WINAPI *winapi_DebugBreakProcess) (HANDLE);
 typedef BOOL (WINAPI *winapi_GenerateConsoleCtrlEvent) (DWORD, DWORD);
 
+#ifdef __x86_64__
+typedef BOOL (WINAPI *winapi_Wow64SetThreadContext) (HANDLE,
+						     const WOW64_CONTEXT *);
+
+winapi_Wow64GetThreadContext win32_Wow64GetThreadContext;
+static winapi_Wow64SetThreadContext win32_Wow64SetThreadContext;
+#endif
+
 #ifndef _WIN32_WCE
 static void win32_add_all_dlls (void);
 #endif
@@ -121,7 +136,12 @@ debug_event_ptid (DEBUG_EVENT *event)
 static void
 win32_get_thread_context (windows_thread_info *th)
 {
-  memset (&th->context, 0, sizeof (CONTEXT));
+#ifdef __x86_64__
+  if (wow64_process)
+    memset (&th->wow64_context, 0, sizeof (WOW64_CONTEXT));
+  else
+#endif
+    memset (&th->context, 0, sizeof (CONTEXT));
   (*the_low_target.get_thread_context) (th);
 #ifdef _WIN32_WCE
   memcpy (&th->base_context, &th->context, sizeof (CONTEXT));
@@ -146,7 +166,14 @@ win32_set_thread_context (windows_thread_info *th)
      it between stopping and resuming.  */
   if (memcmp (&th->context, &th->base_context, sizeof (CONTEXT)) != 0)
 #endif
-    SetThreadContext (th->h, &th->context);
+    {
+#ifdef __x86_64__
+      if (wow64_process)
+	win32_Wow64SetThreadContext (th->h, &th->wow64_context);
+      else
+#endif
+	SetThreadContext (th->h, &th->context);
+    }
 }
 
 /* Set the thread context of the thread associated with TH.  */
@@ -163,7 +190,14 @@ win32_prepare_to_resume (windows_thread_info *th)
 void
 win32_require_context (windows_thread_info *th)
 {
-  if (th->context.ContextFlags == 0)
+  DWORD context_flags;
+#ifdef __x86_64__
+  if (wow64_process)
+    context_flags = th->wow64_context.ContextFlags;
+  else
+#endif
+    context_flags = th->context.ContextFlags;
+  if (context_flags == 0)
     {
       th->suspend ();
       win32_get_thread_context (th);
@@ -195,7 +229,14 @@ child_add_thread (DWORD pid, DWORD tid, HANDLE h, void *tlb)
   if ((th = thread_rec (ptid, DONT_INVALIDATE_CONTEXT)))
     return th;
 
-  th = new windows_thread_info (tid, h, (CORE_ADDR) (uintptr_t) tlb);
+  CORE_ADDR base = (CORE_ADDR) (uintptr_t) tlb;
+#ifdef __x86_64__
+  /* For WOW64 processes, this is actually the pointer to the 64bit TIB,
+     and the 32bit TIB is exactly 2 pages after it.  */
+  if (wow64_process)
+    base += 2 * 4096; /* page size = 4096 */
+#endif
+  th = new windows_thread_info (tid, h, base);
 
   add_thread (ptid, th);
 
@@ -345,8 +386,31 @@ do_initial_child_stuff (HANDLE proch, DWORD pid, int attached)
 
   memset (&current_event, 0, sizeof (current_event));
 
+#ifdef __x86_64__
+  BOOL wow64;
+  if (!IsWow64Process (proch, &wow64))
+    {
+      DWORD err = GetLastError ();
+      error ("Check if WOW64 process failed (error %d): %s\n",
+	     (int) err, strwinerror (err));
+    }
+  wow64_process = wow64;
+
+  if (wow64_process
+      && (win32_Wow64GetThreadContext == nullptr
+	  || win32_Wow64SetThreadContext == nullptr))
+    error ("WOW64 debugging is not supported on this system.\n");
+
+  ignore_first_breakpoint = !attached && wow64_process;
+#endif
+
   proc = add_process (pid, attached);
-  proc->tdesc = win32_tdesc;
+#ifdef __x86_64__
+  if (wow64_process)
+    proc->tdesc = wow64_win32_tdesc;
+  else
+#endif
+    proc->tdesc = win32_tdesc;
   child_init_thread_list ();
   child_initialization_done = 0;
 
@@ -416,10 +480,17 @@ continue_one_thread (thread_info *thread, int thread_id)
 
       if (th->suspended)
 	{
-	  if (th->context.ContextFlags)
+	  DWORD *context_flags;
+#ifdef __x86_64__
+	  if (wow64_process)
+	    context_flags = &th->wow64_context.ContextFlags;
+	  else
+#endif
+	    context_flags = &th->context.ContextFlags;
+	  if (*context_flags)
 	    {
 	      win32_set_thread_context (th);
-	      th->context.ContextFlags = 0;
+	      *context_flags = 0;
 	    }
 
 	  th->resume ();
@@ -943,7 +1014,14 @@ win32_process_target::resume (thread_resume *resume_info, size_t n)
     {
       win32_prepare_to_resume (th);
 
-      if (th->context.ContextFlags)
+      DWORD *context_flags;
+#ifdef __x86_64__
+      if (wow64_process)
+	context_flags = &th->wow64_context.ContextFlags;
+      else
+#endif
+	context_flags = &th->context.ContextFlags;
+      if (*context_flags)
 	{
 	  /* Move register values from the inferior into the thread
 	     context structure.  */
@@ -959,7 +1037,7 @@ win32_process_target::resume (thread_resume *resume_info, size_t n)
 	    }
 
 	  win32_set_thread_context (th);
-	  th->context.ContextFlags = 0;
+	  *context_flags = 0;
 	}
     }
 
@@ -1032,12 +1110,19 @@ win32_add_one_solib (const char *name, CORE_ADDR load_addr)
 
 typedef BOOL (WINAPI *winapi_EnumProcessModules) (HANDLE, HMODULE *,
 						  DWORD, LPDWORD);
+#ifdef __x86_64__
+typedef BOOL (WINAPI *winapi_EnumProcessModulesEx) (HANDLE, HMODULE *, DWORD,
+						    LPDWORD, DWORD);
+#endif
 typedef BOOL (WINAPI *winapi_GetModuleInformation) (HANDLE, HMODULE,
 						    LPMODULEINFO, DWORD);
 typedef DWORD (WINAPI *winapi_GetModuleFileNameExA) (HANDLE, HMODULE,
 						     LPSTR, DWORD);
 
 static winapi_EnumProcessModules win32_EnumProcessModules;
+#ifdef __x86_64__
+static winapi_EnumProcessModulesEx win32_EnumProcessModulesEx;
+#endif
 static winapi_GetModuleInformation win32_GetModuleInformation;
 static winapi_GetModuleFileNameExA win32_GetModuleFileNameExA;
 
@@ -1055,12 +1140,21 @@ load_psapi (void)
 	return FALSE;
       win32_EnumProcessModules =
 	      GETPROCADDRESS (dll, EnumProcessModules);
+#ifdef __x86_64__
+      win32_EnumProcessModulesEx =
+	      GETPROCADDRESS (dll, EnumProcessModulesEx);
+#endif
       win32_GetModuleInformation =
 	      GETPROCADDRESS (dll, GetModuleInformation);
       win32_GetModuleFileNameExA =
 	      GETPROCADDRESS (dll, GetModuleFileNameExA);
     }
 
+#ifdef __x86_64__
+  if (wow64_process && win32_EnumProcessModulesEx == nullptr)
+    return FALSE;
+#endif
+
   return (win32_EnumProcessModules != NULL
 	  && win32_GetModuleInformation != NULL
 	  && win32_GetModuleFileNameExA != NULL);
@@ -1084,10 +1178,19 @@ win32_add_all_dlls (void)
     return;
 
   cbNeeded = 0;
-  ok = (*win32_EnumProcessModules) (current_process_handle,
-				    DllHandle,
-				    sizeof (HMODULE),
-				    &cbNeeded);
+#ifdef __x86_64__
+  if (wow64_process)
+    ok = (*win32_EnumProcessModulesEx) (current_process_handle,
+					DllHandle,
+					sizeof (HMODULE),
+					&cbNeeded,
+					LIST_MODULES_32BIT);
+  else
+#endif
+    ok = (*win32_EnumProcessModules) (current_process_handle,
+				      DllHandle,
+				      sizeof (HMODULE),
+				      &cbNeeded);
 
   if (!ok || !cbNeeded)
     return;
@@ -1096,13 +1199,53 @@ win32_add_all_dlls (void)
   if (!DllHandle)
     return;
 
-  ok = (*win32_EnumProcessModules) (current_process_handle,
-				    DllHandle,
-				    cbNeeded,
-				    &cbNeeded);
+#ifdef __x86_64__
+  if (wow64_process)
+    ok = (*win32_EnumProcessModulesEx) (current_process_handle,
+					DllHandle,
+					cbNeeded,
+					&cbNeeded,
+					LIST_MODULES_32BIT);
+  else
+#endif
+    ok = (*win32_EnumProcessModules) (current_process_handle,
+				      DllHandle,
+				      cbNeeded,
+				      &cbNeeded);
   if (!ok)
     return;
 
+  char system_dir[MAX_PATH];
+  char syswow_dir[MAX_PATH];
+  size_t system_dir_len = 0;
+  bool convert_syswow_dir = false;
+#ifdef __x86_64__
+  if (wow64_process)
+#endif
+    {
+      /* This fails on 32bit Windows because it has no SysWOW64 directory,
+	 and in this case a path conversion isn't necessary.  */
+      UINT len = GetSystemWow64DirectoryA (syswow_dir, sizeof (syswow_dir));
+      if (len > 0)
+	{
+	  /* Check that we have passed a large enough buffer.  */
+	  gdb_assert (len < sizeof (syswow_dir));
+
+	  len = GetSystemDirectoryA (system_dir, sizeof (system_dir));
+	  /* Error check.  */
+	  gdb_assert (len != 0);
+	  /* Check that we have passed a large enough buffer.  */
+	  gdb_assert (len < sizeof (system_dir));
+
+	  strcat (system_dir, "\\");
+	  strcat (syswow_dir, "\\");
+	  system_dir_len = strlen (system_dir);
+
+	  convert_syswow_dir = true;
+	}
+
+    }
+
   for (i = 1; i < ((size_t) cbNeeded / sizeof (HMODULE)); i++)
     {
       MODULEINFO mi;
@@ -1118,7 +1261,22 @@ win32_add_all_dlls (void)
 					 dll_name,
 					 MAX_PATH) == 0)
 	continue;
-      win32_add_one_solib (dll_name, (CORE_ADDR) (uintptr_t) mi.lpBaseOfDll);
+
+      const char *name = dll_name;
+      /* Convert the DLL path of 32bit processes returned by
+	 GetModuleFileNameEx from the 64bit system directory to the
+	 32bit syswow64 directory if necessary.  */
+      std::string syswow_dll_path;
+      if (convert_syswow_dir
+	  && strncasecmp (dll_name, system_dir, system_dir_len) == 0
+	  && strchr (dll_name + system_dir_len, '\\') == nullptr)
+	{
+	  syswow_dll_path = syswow_dir;
+	  syswow_dll_path += dll_name + system_dir_len;
+	  name = syswow_dll_path.c_str();
+	}
+
+      win32_add_one_solib (name, (CORE_ADDR) (uintptr_t) mi.lpBaseOfDll);
     }
 }
 #endif
@@ -1221,8 +1379,10 @@ maybe_adjust_pc ()
   th->stopped_at_software_breakpoint = false;
 
   if (current_event.dwDebugEventCode == EXCEPTION_DEBUG_EVENT
-      && (current_event.u.Exception.ExceptionRecord.ExceptionCode
-	  == EXCEPTION_BREAKPOINT)
+      && ((current_event.u.Exception.ExceptionRecord.ExceptionCode
+	   == EXCEPTION_BREAKPOINT)
+	  || (current_event.u.Exception.ExceptionRecord.ExceptionCode
+	      == STATUS_WX86_BREAKPOINT))
       && child_initialization_done)
     {
       th->stopped_at_software_breakpoint = true;
@@ -1684,13 +1844,34 @@ win32_process_target::qxfer_siginfo (const char *annex,
   if (readbuf == nullptr)
     return -1;
 
-  if (offset > sizeof (siginfo_er))
+  char *buf = (char *) &siginfo_er;
+  size_t bufsize = sizeof (siginfo_er);
+
+#ifdef __x86_64__
+  EXCEPTION_RECORD32 er32;
+  if (wow64_process)
+    {
+      buf = (char *) &er32;
+      bufsize = sizeof (er32);
+
+      er32.ExceptionCode = siginfo_er.ExceptionCode;
+      er32.ExceptionFlags = siginfo_er.ExceptionFlags;
+      er32.ExceptionRecord = (uintptr_t) siginfo_er.ExceptionRecord;
+      er32.ExceptionAddress = (uintptr_t) siginfo_er.ExceptionAddress;
+      er32.NumberParameters = siginfo_er.NumberParameters;
+      int i;
+      for (i = 0; i < EXCEPTION_MAXIMUM_PARAMETERS; i++)
+	er32.ExceptionInformation[i] = siginfo_er.ExceptionInformation[i];
+    }
+#endif
+
+  if (offset > bufsize)
     return -1;
 
-  if (offset + len > sizeof (siginfo_er))
-    len = sizeof (siginfo_er) - offset;
+  if (offset + len > bufsize)
+    len = bufsize - offset;
 
-  memcpy (readbuf, (char *) &siginfo_er + offset, len);
+  memcpy (readbuf, buf + offset, len);
 
   return len;
 }
@@ -1760,4 +1941,12 @@ initialize_low (void)
 {
   set_target_ops (&the_win32_target);
   the_low_target.arch_setup ();
+
+#ifdef __x86_64__
+  /* These functions are loaded dynamically, because they are not available
+     on Windows XP.  */
+  HMODULE dll = GetModuleHandle (_T("KERNEL32.DLL"));
+  win32_Wow64GetThreadContext = GETPROCADDRESS (dll, Wow64GetThreadContext);
+  win32_Wow64SetThreadContext = GETPROCADDRESS (dll, Wow64SetThreadContext);
+#endif
 }
diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index b3fa392..a023eb1 100644
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -27,6 +27,14 @@ struct target_desc;
 /* The inferior's target description.  This is a global because the
    Windows ports support neither bi-arch nor multi-process.  */
 extern const struct target_desc *win32_tdesc;
+#ifdef __x86_64__
+extern const struct target_desc *wow64_win32_tdesc;
+
+extern bool wow64_process;
+
+typedef BOOL (WINAPI *winapi_Wow64GetThreadContext) (HANDLE, PWOW64_CONTEXT);
+extern winapi_Wow64GetThreadContext win32_Wow64GetThreadContext;
+#endif
 
 struct win32_target_ops
 {
@@ -34,7 +42,7 @@ struct win32_target_ops
   void (*arch_setup) (void);
 
   /* The number of target registers.  */
-  int num_regs;
+  int (*num_regs) (void);
 
   /* Perform initializations on startup.  */
   void (*initial_stuff) (void);